1. Field of the Invention
The invention relates to a brake operating device with a means for readjusting a brake, in particular a vehicle brake, where a brake lever is furnished, which brake lever performs together with a brake shaft a pivoting motion around a rotation axis of the brake shaft, which pivoting motion results in an actuation of a brake in the sense of an overcoming of a brake release gap for the purpose of engaging of a brake lining at two brake drums. 2. Brief Description of the Background of the Invention Including Prior Art
A device of the kind recited above is known from the German Patent DE-PS 1,480,038. The known device includes a slack readjustment device, which allows to adjust the position of parts of a brake actuator relative to each other, namely adjusting the position of a brake linkage rod and of a brake lever disposed on the brake shaft. The adjustment serves to provide a continuous readjustment of the position of the parts of the brake actuator in the sense of a maintaining of a preset brake release gap. This readjustment is performed to assure a uniform response behavior of the brakes or, respectively, a uniform brake behavior which, last but not least, is subject matter of corresponding legal and/or regulatory requirements regarding driving safety.
Wear of defects of the slack readjustment device and of its actuating mechanism can, however, effect a deficient readjustment with the consequence that the brake release gap, predefined by the brake type, can no longer be maintained in the course of the driving operation and then does no longer correspond to the actual brake lining wear. A defective readjustment or a complete lack of a readjustment is recognizable in the recited device only by a changing brake actuating stroke, by a decrease in the braking effect, or by a failing of the braking effect. However, this undesired change of the brake release gap occurs only gradually and usually over a longer period of time and is therefore initially hardly perceivable. Therefore, there exists a need to give the operator the certainty with regard to the actual state of the brake release gap and/or of the wear of the brake lining for safety reasons.
An inductive path generator is taught in the German Printed Patent Publication DE-OS 3,813,691 Al to Rainer Nowak, where a first measurement coil exhibiting measurement inductivity is employed and where a second or redundant measurement coil is furnished for obtaining redundancy, which coils capture the measurement path of a measurement cone.
A device for the display of the brake lining wear of heavy road vehicles such as, for example, trucks, buses, pulling machines or the like is taught in the German Printed Patent Publication DE-OS 2,248,927 to Helmut Hase. The reference teaches to employ a switch 19, actuated by contact pin 15, which is connected to display member.
A brake cylinder is taught in the German Printed Patent Publication DE-OS 3,836,080 Al to Josef Frania. An inclined plane is disposed at an axially shiftable radially guided part of a piston, and the contact pin of an electrical path sensor engages the inclined face. An automatic readjustment device for the spread cam of a drum is taught in the German Patent DE 3,625,107 Cl to Georg Sulzyc et al. The coupling exhibits a coupling ring which is rotatably disposed on a worm shaft. A brake device acts on the worm shaft, where the brake device is formed of a second coupling formed as a free wheel and which allows free motion in an opposite rotary sense relative to the first coupling 5,6,7,8.
The German Printed Patent Document DE-OS 1,455,913 to Leo Goldman et al. teaches a device for the display of the wear of brake linings. The reference teaches a rotary mounted cam shaft, which carries a cam disposed between spreadable brake shoes. The brake shoes are furnished with brake linings. The brake linings can come to a rest position at a drum. An adjustment lever, adjustable in a rotary manner, is connected to the cam shaft.
The Austrian Patent 271,236 teaches a display device for an automatically adjusting of a brake lever. An electrical contact arrangement is furnished at a brake lever 1 and at a brake cam shaft for a current circuit containing a display device such that as soon as the brake lever is adjusted versus the brake cam shaft by a rotary angle corresponding to a maximum permissible wear of the brake linings then the contact arrangement of the indicator apparatus is turned on.
The U.S. Pat. No. 2,379,796 to Leon T. Freeman et al. teaches a brake operating mechanism. A pointer 46 is secured on a shaft by a locknut 41 where the pointer cooperates with a scale 48 on the outer end plate 25 of the casing to indicate the adjusted position of the cam. It appears that this scale is used to indicate the wear of a brake lining.